This invention relates to a process of producing a mechanically alloyed composite powder wherein a mixture of powders is prepared which consist of materials which in a liquid state are only partly soluble or are insoluble in each other, said mixture consists of at least one metallic powder and at least one non-metallic powder or consists of a plurality of different metallic powders, said mixture is ground in a drum mill in an operation in which a large quantity of energy is introduced into the mixture being ground, and the atmospheric and/or temperature conditions under which the mixture is ground are optionally controlled.
Mechanical alloying operations can be carried out to produce composite powders which comprise a metallic matrix in which very fine metallic or non-metallic particles are dispersed with a small particle spacing. The process has been used to produce alloys having components which in a molten state are not adequately soluble in each other and/or exhibit an undesired segregation as the mixture solidifies. During mechanical alloying operations, metallic powders and one or more components, such as a high-melting oxide powder or another metal powder, are ground in a drum mill, in which a large amount of energy is introduced into the material being ground. In that operation the powder particles are rolled out by the grinding elements to form thin foils or are disintegrated by said grinding elements and the thin foils are continually bonded by welding. Owing to the high energy supplied, an equilibrium between the bonding of the powder particles and their disintegration is soon achieved so that a composite powder having a uniform particle size and constituting a highly homogenous dispersion is usually obtained. The grinding operation results in the formation of identically composed, composite powder particles which in most cases are laminated. As the grinding operation proceeds, the thickness of the individual layers decreases and the number of layers in each powder particle gradually increases. Mechanical alloying operations may be carried out to alloy not only ductile metals with each other but also to introduce brittle and/or non-metallic components in a state of fine division into a metallic matrix. The grinding operation is performed in conventional ball mills or in attritors and with an optional control of the atmospheric and/or temperature conditions. A grinding operation resulting in a composite powder which is homogenized to the desired degree will take much longer in a grinding mill than in an attritor. But both grinding units are virtually unable to produce mechanically alloyed composite powder particles having reproducible properties for mechanical technology. Besides, the components of the above-mentioned grinding units are subjected to considerably wear.